But Miller and Licklider seem to have been the first discoverers in
1950. Several other investigators, unaware of the earlier
publications, made their own independent discoveries.

thank you for the information. By the way, I would like to inform list
members that the Vicario's paper has been recently scanned and it's
available in pdf format.

Morover, it has also been scanned the original Bozzi and Vicario paper
that, as far as I know, is the first example of stream segregation
(simply look at the figures in the paper: they are self explaining).
[Bozzi, P., & Vicario, G. (1960). Due fattori di unificazione fra note
musicali: la vicinanza temporale e la vicinanza tonale. Rivista di
Psicologia, ann. LIV, n. IV, 235-258]

Here is the link. For those interested look at the first references listed: